After purchasing my
NCE system with an encoder wheel in my radio Procab, I found I was not
completely happy operating with the speed buttons or encoder wheel. In the
System manual I found instructions that explained how to fit a potentiometer
instead of the encoder.

For those that dont
understand, a potentiometer has min and max physical stops just like were used
to on our DC cabs and the encoder has no stops. Operate up to increase speed
and the rate that the wheel is move determines the rate of speed step changes
until max. The wheel still turns but the display stays on max. When decreasing
to stop, the same method applies.

I figured that this
potentiometer could be fitted some where else with a knob. I pulled my Procab
apart and found a really convenient location and only making a small change to
the circuit board to fit it in, under the right hand lower corner of the
display, next to the momentum button.

I purchased the
recommended potentiometer as stated in the System Manual.

Removed the
circuit board and cut off the unused corner for potentiometer access.

Connected the
potentiometer to the circuit board with 3 core shielded wire with the shield
connected to the negative battery terminal.

I initially wired
up the potentiometer with 3 loose wires and I had a display problem, that
sometimes when reducing throttle speed to stop, the loco stopped but the
display still showed about 020 030. Strange, I thought that is was a
shielding problem, so I wired with shielded wire, but made no difference.
This problem still exists but does not cause any operational problem.

The new Procab
has a newer different circuit board.

The radio board
harness connection to the main board is where I previously removed the corner
to allow fitting of the potentiometer.

The blue
potentiometer is shown placed in the position similar to where I fitted in my
modified Procab.

I am not sure
about the capability of adding a potentiometer to this Procab.

Will let you know
with by placing the information here.

I drilled a hole
in the Procab top cover, determined by the available access for the
potentiometer.

Securing the knob
onto the potentiometer shaft will require a matching sleeve to allow knob
fitment.

Glue the sleeve
onto the shaft with super glue making sure no glue flows into the internals
of the pot.

Secure the knob
with its screw. Be careful not to apply too much pressure on the delicate
potentiometer stops.

May be a good
practice not to glue, just have a tight fit so any pressure the knob rotates
as I have done wit mine.

When fitting the
potentiometer you have to add a 2.2 K ohm resistor to the circuit board where
config is written on the board. This now tells the PIC that you have a
potentiometer.

A newer REV D
circuit board. Ill
let you know when I fit the pot/knob as shown in the newer position below.

I seem to
remember asking Larry at NCE about fitting potentiometers to later throttles
and I think he said NO.

The Procab now
operates one handed in the left hand, thumb operating the knob and direction
button. I really like this knob installation. For new operators they hold the
Procab in their left hand and operate the knob with their right hand.

I fitted a 23 mm
knob, could be a little smaller, But this size allows for easy one fingered
operation.

Another Knob location for the Procabs
using both the Encoder and Potentiometer.

In this installation the knob was placed where the
speed wheel is.

The original encoder was used, that is the right
size to fit without too many modifications.

With the knob like this, the encoder is easily
bumped and could cause inadvertent movement of the selected loco.

A better arrangement would to use an encoder similar
to what is in the Cab04E that has mechanical clicks that result in a little
resistance to movement. The Cab04E encoder would only fit with quite a bit of
modification of the circuit board around the wheel slot.

Looks a bit more professional than my first attempt.
Ill let my
operators be the judge and see which of all the Procabs, is better.

I had to cut out some of the housing around the slot
to fit the encoder in, so the circuit board would sit down correctly.

The flanges that centre the wheel and what it rolls
on can foul the encoder. If you remove these, putting the Procab back to its
original position, if not youre not happy with the knob encoder, may cause a
problem.

The encoder in the wheel slot. I filed off some of
the encoder housing and the edge of the circuit board, for more clearance,
too much, hence the white double sided tape over the encoder.

Wired the encoder up to the circuit board as shown.
If speed the wrong way, swap end wires.

As can be seen, the 9.5 mm wide encoder just fits
in. If the wider 12.3 and higher 5.3 mm Cab04E encoder is used, the 2 circuit
board tracks on the left and maybe one on the right will have to be replaced
with wire links.

The 13.2 x 12.3 x 5.3 mm Cab04E Encoder on the left
and the 9.5 x 9.5 x 4.5 mm Procab Encoder on the right showing the larger
size of the Cab04E

Clicker encoder. The slot in the circuit board will
have widened and 2 to 3 tracks replaced by wire links.

I will fit a 20 K potentiometer 9.5 x 9.5 x 4.5 mm
(same size as the encoder), Part No 3310-001-203 to my Procab later as I
prefer the stops and 300 degrees of rotation of a potentiometer.

The completed Knob Encoder Procab showing how easy
it is to use. With the correct knob without a line would be better as it may
give the wrong impression of loco speed for the unwary.

It works quite well, as far as encoders go.

To tighten up the encoder, fit a felt washer or one
made out of sponge, under the knob.